13" Devonian Armored Fish (Coccosteus) Fossil - Scotland

Coccosteus was an arthrodire, belonging to an extinct order of armored, jawed fishes (placoderms) found in Devonian (416 million to 359 million years ago) freshwater and marine deposits. The earliest arthrodires, such as Arctolepis, were fully armored fishes with flattened bodies. They had hollow, backward-curved shoulder spines that may have bene used to anchor themselves or to move about on the bottom of their respective underwater environments.

Later arthrodires such as this Coccosteus were less heavily armored, and the bony head and body shields were connected by a joint on each side for free head movement. They were predators with bony jaws optimized for incredible crushing bite force. The upper jaw was lined with two toothplates per side, whereas the lower jaw had one on each side. The back of the body and the tail were unarmored, and its head shield was reduced, an evolutionary requirement of increasingly predatory habits. Coincidentally, the shoulder spines were also shortened.

The famous “terror of the Devonian seas“(Dunkleosteus) was very similar in appearance to Coccosteus but grew in excess of a whopping 30 feet. By comparison, no Coccosteus has ever been recorded over 2 feet long.